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The LHeC as a Higgs Facility

EPS HEP 2013 Stockholm, July 20th, 2013

Uta Klein (University of Liverpool) for the LHeC Study Group

A Large Hadron Electron Collider at CERN J. Phys. G: Nucl. Part. Phys. 39 (2012) 075001 [arXiv:1206.2913]

EPS2013, Uta Klein, Higgs@LHeC 2

CDR : About 200 experimentalists and theorists from 69 insStutes

Supported by CERN, ECFA, NuPECC

ContribuSons at EPS2013: An energy recovery electron accelerator for DIS at the LHC by Daniel Schulte High Precision DIS with the LHeC by Amanda Cooper-‐Sarkar The LHeC as an energy fronSer eA collider by Max Klein A new detector for deep inelasSc physics by Peter Kostka et al. (poster) New Physics with the LHeC by Monica d’Onofrio et al. (poster)

h^p://cern.ch/lhec

Physics at a glance


! LHeC : up to 100 to 1000 <mes HERA luminosity! (no pile-‐up)

! Higgs@HERA σ~0.5 I …

! Higgs@LHeC with S/N~1; σ~200 I

!   High precision proton PDFs, also for LHC searches

!   High precision αS to 0.1% challenging laWce QCD…

√s=1.3-‐2 TeV

Light SM Higgs producSon in ep


CC NC

• Scale dependencies of the LO calculaSons are in the range of 5-‐10%. •  NLO QCD correcSons are small, but shape distorSons of kinemaSc distribuSons up to 20%. QED correcSons up to -‐5%.

[J. Blumlein, G.J. van Oldenborgh , R. Ruckl, Nucl.Phys.B395:35-‐59,1993] [B.Jager, arXiv:1001.3789]

Light SM Higgs producSon in ep

ETmiss electrons à

LHC protons à Fwd jet

WWH

electrons à

LHC protons à Fwd jet

FS electron

ZZH

è In ep, direc<on of quark (FS) is well defined.


Electron beam energy

CC e-‐p

CC e+p

NC e-‐p

cross secSon [f]

109

58 20

polarised cross secSon [f] P=-‐80%

196 N.A. 25

Ee=60 GeV : √s= 1.3 TeV

MH=125 Ge

V

Hà bb study: Analysis framework

n  Calculate cross sec<on with tree-‐level Feynman diagrams (PDF CTEQ6L1)

n  Generate final state of outgoing par<cles

Event genera<on

by MadGraph/MadEvent

•  SM Higgs produc<on •  CC & NC background

•  Fragmenta<on •  Hadroniza<on

Fast detector simula<on by PGS (LHC-‐style detector)

H → bb selec<on

Input parameters for ini<al studies (CC e-‐p) for the CDR (before Higgs discovery):

n  150 GeV electron beam [ 60 GeV configura<on as comparison]

n  7 TeV proton beam n  120 GeV SM Higgs boson mass

Generator level cuts n  pT > 5 GeV (for partons besides b) n  |η| < 5.0 n  For NC: Number of b quarks ≧ 2

by PYTHIA (modified for ep)


Generated samples Background (examples)

CC: 3 jets (~57 pb) CC: single top produc<on (~4.1 pb)

CC: Z produc<on (~0.11 pb)

NC: b pair produc<on (~1.1 nb)

Signal

CC: H → bb (BR ~ 0.7 at MH=120GeV)

σ~ 0.16 pb at √s=2.05TeV

NOTE: Background sample numbers are a}er pre-‐selec<on in generator


SelecSon of H→bb n  NC DIS rejec<on

n  Exclude electron-‐tagged events n  ET,miss > 20 GeV n  Njet (pT > 20 GeV) ≧ 3 n  ET,total > 100 GeV n  yJB < 0.9, Q2

JB > 400 GeV2

n  b-‐tag requirement n  Nb-‐jet (pT > 20 GeV) ≧ 2

n  Higgs invariant mass n  90 < MH < 120 GeV

n  Single top rejec<on n  Mjjj,top > 250 GeV n  Mjj,W > 130 GeV

ETmiss cut b-tag requirement

H→bb CC BG NC BG

⇒ 44% of remaining BG is single-‐top…

⇒10% mis-‐ID


H→bb results [MH=120 GeV, Ep=7 TeV] Forward jet η tag H → bb signal n  Forward jet tagging

n  ηjet > 2 (lowest η jet excluding b-‐tagged jets)

n  Higgs invariant mass a}er all selec<on

H→bb CC BG NC BG

Coordinate: Fwd: +z-‐axis along proton beam

Z→bb

Ee=150 GeV

10 I-‐1

Clear signal obtained with cut-‐and-‐count based analysis!


H→bb results [MH=120 GeV, Ep=7 TeV]

Ee=60 GeV

Ee = 150 GeV (10 f-‐1)

Ee = 60 GeV (100 f-‐1)

H → bb signal 84.6 248

S/N 1.79* 1.05

S/√N 12.3 16.1

10 I-‐1

n  Case study for electron beam energy of 60 GeV using same analysis strategy n  luminosity values of 100 I-‐1 are feasible

n  Electron energy recovery LINAC with high electron polarisa<on of 80% and 1034 cm-‐2 s-‐1 è enhancement by factor 18 feasible, i.e. around 4500 Higgs candidates for Ee=60 GeV allowing to measure Hbb coupling with 0.8 % sta<s<cal precision.

n  S/N ~1 confirmed in independent analysis for MH=125 GeV for Ee=60 GeV (master thesis by Sergio Mandelli, University of Liverpool 2013)

*Note: A parton-‐level study delivered S/N of 4.7.


… as a Higgs “Facility” @ 1 ab-‐1 à for first Sme a realisSc opSon of an 1 ab-‐1 ep collider (stronger e-‐source, stronger focussing magnets) and excellent performance of LHC (higher brightness of proton beam); ERL : 960 superconduc<ng cavi<es (20 MV/m) and 9 km tunnel [arXiv:1211.5102, arXiv:1305.2090; talk by D. Schulte]


Ul<mate e and p beams, 10 years of opera<on

è other BR’s started to be explored, e.g. ττ

Measure CP properSes of Higgs •  Higgs couplings with a pair of gauge bosons (WW/ZZ) and a pair of heavy fermions

(t/b/τ) are largest. •  Higgs@LHeC allows uniquely to access HWW vertex è explore the CP proper<es

of HVV couplings: BSM will modify CP-‐even (λ) and CP-‐odd ( λ’) states differently

•  Study shape changes in DIS normalised CC Higgsà bb cross sec<on versus the azimuthal angle, ΔφMET,J, between ET,miss and forward jet.

In ep, full Δφ range can be explored, here not shown yet.

è


CDR iniSal study of HWW vertex: CP couplings probed to λ~0.05 λ’~0.2 based on 50 f-‐1

Partons for LHC Higgs


44

46

48

50

52

54

56

58

60

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

à Using LHeC input: experimental uncertainty of predicted LHC Higgs cross sec<on is strongly reduced to 0.4% due to PDFs and αS è clear Higgs mass sensi<vity in cross sec<on predic<ons. è Higgs@LHC with

σ(H)~50 pb è HL-‐LHC + ep Higgs

potenSal and PDFs and αS : transform the LHC facility into a genuine Higgs factory

LHeC

Summary


! LHeC, in ep(A) collisions synchronous with pp (AA) running, could deliver

fundamentally new insights on the structure of the proton (and nucleus) and the strong coupling αS with high precision è thus strengthen enormously the HL/HE-‐LHC physics case for searches [“On the Rela<on of the LHeC and the LHC”, arXiv:1211.5102]

!   Sensi<vity to H→bb is es<mated by an ini<al simula<on study : LHeC has the poten<al to measure H → bb coupling with an S/N of ~1 and to 1% (4%) accuracy with 60 GeV electron beam based on a luminosity of 1034 (1033) cm-‐2 s-‐1.

!   At LHeC, various Higgs boson decays and Higgs CP eigenstates could be accessed via WW and ZZ fusion at c.m.s. energies of 1.3 TeV and with 1 ab-‐1 -‐ complementary to LHC experiments.

!   New high luminosity prospects in ep have just started to be explored and

open exciSng new potenSal for complementary, precision Higgs physics at the LHC facility.

AddiSonal material


CDR review process

16

International referees invited by CERN

… put to scale

17

è synchronous running of ep and pp a}er LS3 as an upgrade op<on of the HL-‐LHC

18

60 GeV Electron Accelerator

ICHEP LHeC Max Klein 7.7.2012 18

Two 1km long LINACs connected at CERN territory Arcs of 1km radius: ~9km tunnel 3 passages with energy recovery

John Osborne (June LHeC Workshop)

LHeC and the HL-‐LHC (SUSY searches)

19

With high energy and luminosity, the LHC search range will be extended to high masses, up to 5 TeV in pair produc<on. At correspondingly high x (> 0.5) the PDFs are unknown to a considerable extent à PDF uncertain<es easily > 100% for high mass searches è gluon density from LHeC (10% at x=0.6, ~4TeV)] The HL-‐LHC (search) programme requires a much more precise understanding of QCD, which the LHeC provides (strong coupling, gluon, valence, factorisa<on, satura<on, diffrac<on..)

KinemaSc distribuSons [MH=120 GeV, Ee=150 GeV, Ep=7 TeV]

a-‐b) Kinema<c distribu<ons of generated Higgs c-‐d) Reconstructed yJB and Q2

JB

pTH ηTH

yJB Q2JB

Generated events passed to Pythia and to generic LHC-‐style detector: n  Coverage:

n  Tracking: |η| < 3 n  Calorimeter: |η| < 5

n  Calorimeter resolu<on n  EM: 1% ⊕ 5%/√E n  Hadron: 60%/√E n  Cell size: (Δη,Δφ) = (0.03, 0.03)

n  Jet reconstructed (cone ΔR=0.7) n  b-‐tag performance

n  Flat efficiency for |η| < 3 n  Efficiency/mis-‐ID

n  b-‐jet: 60% n  c-‐jet: 10% n  Other jets: 1%


‘Detector’ LHC ! parameter set name 320 ! eta cells in calorimeter 200 ! phi cells in calorimeter 0.0314159 ! eta width of calorimeter cells |eta| < 5 0.0314159 ! phi width of calorimeter cells 0.01 ! electromagnetic calorimeter resolution const 0.2 ! electromagnetic calorimeter resolution * sqrt(E) 0.8 ! hadronic calolrimeter resolution * sqrt(E) 0.2 ! MET resolution 0.01 ! calorimeter cell edge crack fraction cone ! jet finding algorithm (cone or ktjet) 5.0 ! calorimeter trigger cluster finding seed threshold (GeV) 1.0 ! calorimeter trigger cluster finding shoulder threshold (GeV) 0.5 ! calorimeter kt cluster finder cone size (delta R) 2.0 ! outer radius of tracker (m) 4.0 ! magnetic field (T) 0.000013 ! sagitta resolution (m) 0.98 ! track finding efficiency 1.00 ! minimum track pt (GeV/c) 3.0 ! tracking eta coverage 3.0 ! e/gamma eta coverage 2.4 ! muon eta coverage 2.0 ! tau eta coverage

20%à 5% 80%à60%

jets: cone<0.7

Disclaimer : PGS of LHC detector + flat b-‐tagging in the full tracking range of |η|<3.0 b: 60%, c: 10%, udsg: 1% CAL coverage un<l |η|<5.0 EPS2013, Uta Klein, Higgs@LHeC 21

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